They smashed up the "hockey stick" at Climate Audit on Sunday. The "hockey stick" is a chart developed by Michael Mann et al. ten years ago that showed that global temperatures were pretty constant until about 100 years ago when they began to shoot up (hence "hockey stick"). It was based on a statistical analysis of numerous temperature "proxies" such as tree ring width on bristle-cone pine trees.
Willis Eschenbach of climateaudit.org did some statistical analysis of his own. He asked: which of the Mannian temperature proxies actually carry the "hockey-stick" signal?
The answer was devastating. Out of the 95 data series in the latest Mann paper that covered the entire last 1,000 years, only 25 carried the "hockey stick" signal. Three of these series are lake sediments in Finland which are corrupted by recent urban development and the rest are from bristle-cone pine trees in the US Southwest that have been challenged by other researchers.
Take the "hockey stick" proxies out and you get a signal that shows a Medieval Warming Period a thousand years ago and a Little Ice Age 300 years ago. What a surprise!